This application is related to copending and commonly-assigned U.S. patent application Ser. No. 09/250,453, entitled xe2x80x9cAPPARATUS, SYSTEM, AND METHOD FOR OPTIMIZING THE DESIGN OF SLIDER PROTRUSIONS IN A HARD DISC DRIVE SYSTEMxe2x80x9d, filed Feb. 16, 1999, by Thomas R. Pitchford, et al., which application is incorporated by reference herein.
The present invention relates to the field of mass storage devices. More particularly, this invention relates to a slider for use in a disk drive which includes landing pads for minimizing stiction and wear for the slider.
One of the key components of any computer system is a place to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disk drive. The most basic parts of a disk drive are a disk that is rotated, an actuator that moves a transducer to various locations over the disk, and electrical circuitry that is used to write and read data to and from the disk. The disk drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disk surface. A microprocessor controls most of the operations of the disk drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disk.
The transducer is typically housed within a small ceramic block. The small ceramic block is passed over the disk in a transducing relationship with the disk. The transducer can be used to read information representing data from the disk-, or write information representing data to the disk. When the disk is operating, the disk is usually spinning at relatively high RPM. These days common rotational speeds are 7200 RPM. Some rotational speeds are as high as 10,000 RPM. Higher rotational speeds are contemplated for the future. These high rotational speeds place the small ceramic block in high air speeds. The small ceramic block, also referred to as a slider, is usually aerodynamically designed so that it flies over the disk. The best performance of the disk drive results when the ceramic block is flown as closely to the surface of the disk as possible. Today""s small ceramic block or slider is designed to fly on a very thin layer of gas or air. In operation, the distance between the small ceramic block and the disk is very small. Currently xe2x80x9cflyxe2x80x9d heights are about 12 microinches. In some disk drives, the ceramic block does not fly on a cushion of air but rather passes through a layer of lubricant on the disk.
Information representative of data is stored on the surface of the memory disk. Disk drive systems read and write information stored on tracks on memory disks. Transducers, in the form of read/write heads, located on both sides of the memory disk, read and write information on the memory disks when the transducers are accurately positioned over one of the designated tracks on the surface of the memory disk. The transducer is also said to be moved to a target track. As the memory disk spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the memory disk. Similarly, reading data on a memory disk is accomplished by positioning the read/write head above a target track and reading the stored material on the memory disk. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disk drives, the tracks are a multiplicity of concentric circular tracks. In other disk drives, a continuous spiral is one track on one side of a disk drive. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held very accurately during a read or write operation using the servo information.
Disk drives have actuator assemblies which are used to position the slider and transducer at desired positions with respect to the disk. The slider is attached to the arm of the actuator assembly. A cantilevered spring, known as a load spring, is typically attached to the actuator arm of a disk drive. The slider is attached to the other end of the load spring. A flexure is attached to the load spring and to the slider. The flexure allows the slider to pitch and roll so that the slider can accommodate various differences in tolerance and remain in close proximity to the disk. The slider has an air-bearing surface (xe2x80x9cABSxe2x80x9d) which includes rails and a cavity between the rails. The air-bearing surface is that portion of the slider that is nearest the disk as the disk drive is operating. When the disk rotates, air is dragged between the rails and the disk surface causing pressure, which forces the head away from the disk. At the same time, the air rushing past the depression in the airbearing surface produces a negative pressure area at the depression. The negative pressure or suction counteracts the pressure produced at the rails. The different forces produced counteract and ultimately the slider flies over the surface of the disk at a particular fly height. The fly height is the thickness of the air lubrication film or the distance between the disk surface and the head. This film eliminates the friction and resulting wear that would occur if the transducing head and disk were in mechanical contact during disk rotation.
One of the most critical times during the operation of a disk drive is just before the disk drive shuts down. The small ceramic block is typically flying over the disk at a very low height when shutdown occurs. The slider is typically moved to a non-data area of the disk where it literally landed and skidded to a stop on the disk surface. Disk drives that park the slider on a non-data area of the disks have problems. The problem is static friction which is also known as stiction. In the past, the non-data area of the disk was textured or otherwise roughened so that there would be less chance of stiction between the slider and the disk. In some instances, lasers were used to form specific textures at the landing areas of the disk.
Currently disk drives use smooth disk surfaces. In other words, the disk is not textured at any location. Stiction problems increase when using the smooth disks. When the sliders are parked on the smooth surface of the disk, stiction results between the slider, a small ceramic block, and the disk surface. In some instances, the stiction forces are large enough to virtually rip the slider away from the load spring to which the slider is attached. In order to lessen the problems associated with stiction between the disk and the slider, pads have been provided on the air bearing surface. In a paper by Y. Kasamatsu, T. Yamanoto, S. Yoneoka, and Y. Mizoshita, IEEE Transactions on Magnetics, Volume 3 1, page 296 1, issued in 1995, a design using three pads is disclosed. One pad is located near the center pad. The second pad is located on the center of the outside rail. The third pad is located on the center of the inside rail. The disadvantage of this design is that one pad is located near the center pad which houses the read/write transducer such that it may interfere with the normal operation of the read/write head. In other words, the pad near the center pad may alter the flying height of the read/write head and therefore alter the performance of the head. It is well known that the closer the read/write head is to the magnetic recording surface, the better the magnetic performance. Placing a pad near the center pad may result in an increased flying height.
Another disadvantage associated with this design is that there is no consideration of placing the pads to minimize stiction forces. Head-disk interface stiction arises mainly for menisci formed at the contact points between the slider and the disk. The magnitude of this force is proportional to the total area of the meniscus and the pressure within the meniscus which is inversely proportional to the separation between the slider and the disk. When a pad is placed in the center of a rail, a full circle meniscus is formed which allows a full stiction force to be formed at that particular point.
As can be seen, there is a need for a slider having pads placed thereon to minimized any stiction forces that occur. In addition, there is a need for a slider that minimizes stiction overall between the slider and the disk. In addition, there is a need for a slider design that uses pads which do not interfere with the normal operation of the read/write head or transducer associated with the slider. There is still a further need for a robust design that can absorb some of the impact that might occur when the slider lands on the disk. There is still a further need for a slider that can undergo multiple starts and stops of the disk drive without failing over the life of the disk drive.
A disk drive system or information handling system includes a base, a disk stack rotatably attached to the base, and an actuator assembly movably attached to the base. An actuator assembly is movably attached to the base of the disk drive. The actuator assembly moves the load springs and attached slider and transducers to various radial positions on the disk. The slider is a block of material having a leading edge, a trailing edge, a first side rail, a second side rail, a leading tapered edge and a center island. The center island is positioned near the trailing edge and includes the read and write heads or transducer. Sliders have a backside surface and an air-bearing surface. The slider also has one or more pads positioned near the edges of the first rail, the second rail, and the leading tapered edge. The pads are positioned at least a selected distance from the trailing edge. The pads are also positioned such that they are unaligned in the sliding direction. The pads are also positioned so that they are unaligned in the sliding direction when the first side rail and the second side rail form an angle with respect to a tangent at the radial position on the disk. In other words, the pads are unaligned when the slider is skewed with respect to the disk. The pads are formed using photolithography techniques.
Advantageously, the pads are placed on the air-bearing surface of the slider to minimized any stiction forces that occur. The placement of the pads produces a slider that minimizes stiction overall between the slider and the disk. The pads do not interfere with the normal operation of the read/write head or transducer associated with the slider since the pads are offset a selected distance from the trailing edge of the slider. The pads are also unaligned in the sliding direction so that the lubricant on the disk can fill in between successive passes of the slider over a track. The pads are also unaligned in the sliding direction when the slider is skewed with respect to the disk. The end result is a slider that can undergo multiple contact start/stops without failing prematurely. The slider is also easily manufactured using photolithography techniques and the slider is robust and can absorb some of the impact that occurs when the slider lands on the disk.